A flatworm obtains its food through cells on the surface of its body and also through the orifice at the top of the head. The cells absorb nutrients from the water by diffusion, and when digestion is complete, the mouth orifice also serves as the anus.
Flatworms that are living in people or animals do not have the means to digest nutrients as they obtain it from the host, which is already digested. Flatworms are bilateral organisms with a central nervous system and eyes that are able to sense light. They live in freshwater and saltwater as well as on land.